1. Field of the Invention
This invention pertains to the field of electronics. More specifically, this invention pertains to the field of electro-optics. In greater particularity, the invention pertains to an electronic detector of infrared energies. By way of further characterization, by without limitation thereto, the invention shall be described as it pertains to any audio circuit for use in a missile guidance system.
2. Description of the Prior Art
It is known in the missile electronics arts to use a audio signal derived from a detected target to indicate target acquisition or various other missile readiness perimeters. Generally, these signals are derived from the missile signal obtained from the target itself. That is, incoming radiation from the target is modulated by a suitable reticle and pre-photocell optical system such that a characteristic modulation is impressed upon the signal for processing purposes. This signal is then amplified and used to indicate the presence of such a target. A difficult problem exists in a relatively narrow angular target in the presence of background radiation.
Prior attempts to solve this problem have utilized various bucking circuits or separate background and target modulators such that the target signal is indicated by characteristic frequencies or other characteristics imposed upon the target by its position within the field of view of the missile or its position on the reticle.
The present invention uses the harmonics generated by a signal of small angular dimensions to indicate the presence of a target in a background of other radiation. A bandpass filter filters this target energy limiting it to the harmonic content produced by such a small target interacting with the reticle as an initial target signal. This signal is detected and fed to a summing amplifier where it is mixed with a guidance control system audio signal to produce an output in the presence of a target signal. The output of the summing amplifier is connected to a spin frequency filter to develop a sinusoidal output of the desired audio frequency. This output is fed to a multiplier where it modulates a second audio signal to produce an enhanced audio output which is indicative of the acquisition of a target signal.
Accordingly, it is an object of this invention to provide an electronic circuit to produce an audio signal upon the reception of a target having predetermined angular dimensions.
A further object of this invention is to provide an electronic circuit for the production of enhanced audio signal.
A still further object of this invention is to provide an electronic circuit for use in a missile guidance system to indicate the presence of a target signal.